The (rnrs (6)) library is intended as a convenient import for
libraries where fine control over imported bindings is not necessary
or desirable. The (rnrs (6)) library exports all bindings for
expand as well as run so that it is convenient for writing
syntax-case macros as well as run-time code.

The (rnrs (6)) library does not include a few select libraries:

(rnrs eval (6)), as its presence may make creating
self-contained programs more difficult;

(rnrs mutable-pairs (6)), as its absence from a program may enable compiler
optimizations, and as mutable pairs might be deprecated in the future;

(rnrs mutable-strings (6)), for similar reasons as for
(rnrs mutable-pairs (6));